The present invention generally relates to elevator or lift systems and, in particular, concerns a new and improved construction of a start control device or apparatus, especially for an elevator or the like.
The start-up control apparatus of the present development is of the type comprising a drive motor which can be turned-on by means of the closing contacts of a mains or primary protection circuit and an electromechanical holding brake which contains at least one brake magnet and a brake spring. One terminal of the brake magnet is connected by a closing contact of a brake protection circuit with one terminal or pole of a voltage source. The brake magnet, upon turning-on the elevator drive, is energized and the holding brake is lifted or opened against the force of the braking spring.
Simple, economical elevator systems which are driven by asynchronous motors do not possess any inherent start-up control devices. With such type elevator systems known from prior art publications, for instance Bethmann "Der Aufzugsbau," the brake magnet of an electromechanical holding brake is energized by the contacts of the primary protection of the drive motor. Lifting or opening of the holding brake against the action of a weight or a spring occurs, in this case, suddenly upon cutting-in the drive motor. The start-up comfort of such type of elevators is insufficient, since the starting jerk becomes markedly discernable due to the sudden lifting of the brake and the immediate or sudden superimposing of the motor start-up torque or moment and the load moment or torque.
Additionally, it is known in this technology to energize the brake magnets of the holding brake during the elevator start-up by means of the closing contact of a brake protection or brake protection circuit. Thus, for instance, in German Pat. No. 1,091,303 there is disclosed an apparatus wherein the brake protection circuit is energized, upon cut-on, with the aid of an auxiliary contact of the mains protection circuit of the drive motor. As a result there is realized a certain operational integrity or reliability, since the holding brake is first opened or lifted when the drive is turned-on. Additionally, with such an arrangement it is possible to control completely independently of one another the brake and drive motor during the deceleration phase of the elevator. With the state-of-the-art equipment there automatically occurs a delay between the cut-on time point and the start of brake lifting, so that it is not possible however to obtain any appreciable improvement in the start-up comfort.
On the other hand, it is known in this technology to employ an electromechanical holding brake for the regulated braking of an elevator during the deceleration phase for the purpose of exactly stopping the elevator at the required floor or storey of the building or structure. Thus, for instance, the brake apparatus disclosed in German Pat. No. 2,003,951 possesses a regulation circuit embodying a tachometer dynamo forming an actual value from the rotational speed of a shaft which is to be braked, a reference value transmitter containing the braking program, a regulation or control amplifier for comparison of the actual and reference values as well as an adjustment or setting element acting upon a brake magnet.